This invention relates to an electronic musical instrument of a channel assignment type and capable of carrying out an automatic arpeggio performance.
An electronic musical instrument of a channel assignment type is known in the art, in which a plurality (small particular number) of tone production channels are provided and the data of keys depressed from among a larger plurality of keys are assigned to some of the tone production channels, so that a plurality of tones are produced simultaneously through the tone production channels. Such an electronic musical instrument is so designed that the same single key is not assigned to a plurality of tone production channels. One example of the electronic musical instrument of this type is disclosed in the specification of U.S. Pat. No. 4,158,978 entitled "Electronic Musical Instrument". In the electronic musical instrument disclosed in the specification of said U.S. Patent, a chord pyramid performance which is a kind of or somewhat similar to an automatic arpeggio performance is carried out. More specifically, after the tone productions of one or plural keys depressed in the keyboard are assigned individually to one or plural tone production channels, the timings of musical tone productions in the tone production channels are controlled, so that the one or plural tones are sequentially produced one at a time at predetermined time intervals. Accordingly, in the tone production channels to which the keys depressed for the chord pyramid performance (automatic arpeggio performance) have been assigned, the tones are not always produced in response to the key depressions; that is, the tone production is effected only in the tone production channel which has been selected by the tone production timing control, and the tone production channel in which the tone production is actually effected in successively switched (selected). In this case, the number of tone production channels is limited (for instance, to twelve). Accordingly, as the number of keys depressed for the automatic performance is increased, the number of channels in which ordinary tone production is effected just following the key depression is reduced.
In order to eliminate the difficulty described above, Japanese Patent Application No. 1977-106417 entitled "Electronic Musical Instrument" (Open-Laying No. 1979-39621) has been proposed. More specifically, in an electronic musical instrument having a plurality of tone production channels, an exclusive channel is provided for an automatic arpeggio performance, so that automatic arpeggio tones are produced one after another in that exclusive channel. In this case, the tones of keys depressed in the keyboard are produced in the ordinary tone production channels in the usual manner according to the way of the key depressions and additionally are produced selectively in the automatic arpeggio exclusive channel.
However, it should be noted that in the above-described two prior arts and also in any automatic arpeggio performance arts provided before them it is impossible to simultaneously produce two tones or more in arpeggio pattern (i.e. polyphonic arpeggio); that is, the automatic arpeggio performance is so monotonous as only one tone is produced at a time.